Twin Advice: Setting Up The House

Create a changing station on each floor.
This will save you numerous trips up and down the stairs. We just used one of the changing pads anchored to the back of a dresser instead of investing in a whole separate piece of furniture, both in the nursery and downstairs (Summer Infant Contoured Changing Pad). If you don't have room to have a full changing station, it could be as simple as a basket with diapers, wipes, and a changing pad that you keep downstairs. 

Have an area for the babies to nap downstairs for the first few months.
During the first few months, the babies will be in a constant cycle of eating and sleeping, and it is nice to avoid constantly going up and down the stairs. At various times, I used Moses baskets, bouncy seats, and a Pack and Play, all of which worked well. Once the babies are a bit bigger and you are trying to get them onto a schedule, I found that putting them in their cribs worked best.

Have places throughout the house to safely keep one baby while you are are busy feeding, changing, comforting the other (or both babies while you try to eat, shower, etc).
What form this will take will depend on the developmental stage of your babies. Bouncy seats work well for the first 4 months. I literally think at one point I had at least 4 scattered throughout various rooms of my house. We gradually moved on to Bumbo seats, followed by Exersaucers, and then were able to eek out a few more weeks with Jumperoos before they refused to be restrained in any way.

 

Instead of the typical rocker or glider for the nursery, consider getting a bigger chair or even a  loveseat if you have room.
We have a chair-and-a-half that has worked really well. It is large enough that I could comfortably tandem feed using the big nursing pillow and has allowed me to comfortably cuddle with both kids for bedtime stories as they have gotten bigger.